The colourful invader that’s bad news for native species

Just before I got out of bed I was puzzled by what seemed to be a faint clicking noise. When I drew the curtains I was most surprised to find the window covered with probably a hundred or more harlequin ladybirds. This was the last week of March and one of the first warm days after a spell of bitter winds, so I imagine the ladybirds had over-wintered somewhere round the windows and the warmth had moved them into action.

These ladybirds are a little bigger than our native species and are patterned in a large number of ways: orange/red with many black spots, black or black with large red spots and some are even yellowish with any variety of black marking.These insects have characteristic white facial markings.

Although interesting, this find was not at all pleasing. It was really the result of an ill-thought-out interference by man. In 1988 there was an epidemic of insect pests in America and it was known that the Asiatic ladybirds had the ability to control aphids and scale insects, so a number of the ladybirds were sent to America for that purpose.

It is a story we have heard too many times in the past. It seemed a sensible plan but it all went wrong. Plant and plant materials were exported from America to Holland and the ladybirds went with them. By 2004 materials sent from Holland to Britain carried some of the aliens with them and they were rapidly successful enough to become serious pests. They certainly do reduce the aphid population, but, unfortunately, if aphids are scarce they will eat butterfly eggs and our own, smaller native ladybirds and their larvae.

One further point to remember is that these ladybirds can bite, and each female is capable of laying many hundreds of eggs.

Harlequin ladybirds can exude a defensive chemical to deter predators. This is produced from their legs and it has a noticeable disagreeable smell. Any fabric with which the insect is in contact when this chemical is exuded may be stained with this secretion.